What's interesting is that they have only sold 1.5M books, or 1.5 books per device. Amazon Kindle should be safe.
If you ever tried to actually read on an iPad you would understand why. The glossy screen means you can't read in natural light, and the backlit screen causes eye strain. For long stretches of reading, iPad can't replace books the same way the Kindle can. Although I'm personally not surprised that books aren't that popular on iPad, but I was curious if people would overcome the above deficiencies with the form factor…
This is commonly claimed, but I've never seen a cite to any science to back it. All I've been able to find is scientists saying its a myth.